From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B8F5C00143 for ; Wed, 1 Sep 2021 12:45:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 162EA61207 for ; Wed, 1 Sep 2021 12:45:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345757AbhIAMpB (ORCPT ); Wed, 1 Sep 2021 08:45:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:43544 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344974AbhIAMkR (ORCPT ); Wed, 1 Sep 2021 08:40:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CFC09610CE; Wed, 1 Sep 2021 12:36:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1630499786; bh=vcUSTnaYK9xUm+aQ+qSPNWuE10+gFn0zLr5QUjeWSrQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=clEN4J3C2EFmJ/OUUigj5rdYzKzx0ZzYnEw7EL4PLseCS470knKd6xJDenu6+yR5S RGDfISVsCqLaxcKCsFwbfuCXQgd72KCEo16wFD+krZ1KdAOkbomXy95CFvWN3evHAm n4B4P9Rcb0/7oiR2xJyfd74GD9hTWCNCW+7JQn60= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sebastian Andrzej Siewior , Athira Rajeev , Michael Ellerman , Hanjun Guo Subject: [PATCH 5.10 085/103] powerpc/perf: Invoke per-CPU variable access with disabled interrupts Date: Wed, 1 Sep 2021 14:28:35 +0200 Message-Id: <20210901122303.407702613@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210901122300.503008474@linuxfoundation.org> References: <20210901122300.503008474@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Athira Rajeev commit f66de7ac4849eb42a7b18e26b8ee49e08130fd27 upstream. The power_pmu_event_init() callback access per-cpu variable (cpu_hw_events) to check for event constraints and Branch Stack (BHRB). Current usage is to disable preemption when accessing the per-cpu variable, but this does not prevent timer callback from interrupting event_init. Fix this by using 'local_irq_save/restore' to make sure the code path is invoked with disabled interrupts. This change is tested in mambo simulator to ensure that, if a timer interrupt comes in during the per-cpu access in event_init, it will be soft masked and replayed later. For testing purpose, introduced a udelay() in power_pmu_event_init() to make sure a timer interrupt arrives while in per-cpu variable access code between local_irq_save/resore. As expected the timer interrupt was replayed later during local_irq_restore called from power_pmu_event_init. This was confirmed by adding breakpoint in mambo and checking the backtrace when timer_interrupt was hit. Reported-by: Sebastian Andrzej Siewior Signed-off-by: Athira Rajeev Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1606814880-1720-1-git-send-email-atrajeev@linux.vnet.ibm.com Signed-off-by: Hanjun Guo Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/perf/core-book3s.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -1884,7 +1884,7 @@ static bool is_event_blacklisted(u64 ev) static int power_pmu_event_init(struct perf_event *event) { u64 ev; - unsigned long flags; + unsigned long flags, irq_flags; struct perf_event *ctrs[MAX_HWEVENTS]; u64 events[MAX_HWEVENTS]; unsigned int cflags[MAX_HWEVENTS]; @@ -1992,7 +1992,9 @@ static int power_pmu_event_init(struct p if (check_excludes(ctrs, cflags, n, 1)) return -EINVAL; - cpuhw = &get_cpu_var(cpu_hw_events); + local_irq_save(irq_flags); + cpuhw = this_cpu_ptr(&cpu_hw_events); + err = power_check_constraints(cpuhw, events, cflags, n + 1); if (has_branch_stack(event)) { @@ -2003,13 +2005,13 @@ static int power_pmu_event_init(struct p event->attr.branch_sample_type); if (bhrb_filter == -1) { - put_cpu_var(cpu_hw_events); + local_irq_restore(irq_flags); return -EOPNOTSUPP; } cpuhw->bhrb_filter = bhrb_filter; } - put_cpu_var(cpu_hw_events); + local_irq_restore(irq_flags); if (err) return -EINVAL;